1. Field of Invention
The present invention relates to a method for inspecting a polar element, and more particularly, to a method for automatically inspecting polar directions of a polar element on a substrate.
2. Description of Related Art
Generally speaking, many electronic elements are assembled on the printed circuit board by automatic assembly equipment.
However, some electronic elements have a voltage polarity requirement. The correct polarity is indicated on the packaging by a stripe with minus signs and possibly arrowheads for the manual visual inspection. This is necessary because a reverse-bias voltage will destroy polar elements. Taking electrolytic capacitors for example, if one electrolytic capacitor with the reversed polar directions is assembled on the motherboard, the electrolytic capacitor may be destroyed in the electrical character test of the In-Circuit Tester (ICT).
As for the manual visual inspection of the positive and negative polar directions of the electrolytic capacitor, particularly, the tester needs to prefabricate a mask plate with a plurality of through-holes, so as to serve as a standard sample for inspecting The position and size of the plurality of through-holes of the mask plate are determined by the position and size of the electrolytic capacitor on the standard printed circuit board. The positive and negative polar directions of the electrolytic capacitor are marked beside each through-hole on the mask plate. When the tester intends to inspect the polarities of the electrolytic capacitor on a motherboard to be inspected, he/she needs to align the motherboard with the mask plate and then cover the mask plate on the motherboard, such that the electrolytic capacitor is protruded from the mask plate, which is convenient for human eyes to inspect whether the positive and negative polar directions of each electrolytic capacitor are correct or not.
However, since the elements required to be inspected by the tester are not only limited to the electrolytic capacitor, various elements with different sizes on the motherboard are required to be inspected whether their individual inserting positions or the positive and negative polar directions are correct or not. Working for a long time easily makes people feel tired, and it is easy for the tester not to inspect the electrolytic capacitor with reversed polar directions due to carelessness. Therefore, when the tester performs the electrical character test to the motherboard having an electrolytic capacitor with reversed polar directions, the motherboard may be exploded and thereby damaging or burning out a part of the elements thereon, and the yield of the product cannot be maintained.
Moreover, the cost for repairing the exploded motherboard is nearly equal to that for re-fabricating a new motherboard, so the cost for fabricating the product cannot be effectively reduced. Besides, if the motherboard having the electrolytic capacitor with reversed polar directions has been sent to the client, and it is exploded or burnt out when being used by the customer, the customer will not trust the product any longer.